<template>
  <div class="todo-footer" v-show="total">
    <label>
      <input type="checkbox" :checked="isAll" @click="checkAll" />
    </label>
    <span>
      <span>已完成{{ doneTotal }}</span> / 全部{{ total }}
    </span>
    <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
  </div>
</template>

<script>
export default {
  name: "myFooter",
  props: ["todos", "checkAllTodo", "clearAllTodo"],
  computed: {
    total() {
      return this.todos.length;
    },
    doneTotal() {
      //第二次的pre是第一次运行结果的返回值，第一次pre是0但是没有return所以第二次pre=undefined
      //current是每一个todo项

      //  return this.todos.reduce((pre,current)=>{
      //    return pre+(current.done?1:0)
      //  },0)
      return this.todos.reduce(
        (pre, current) => pre + (current.done ? 1 : 0),
        0
      );
      //最后一次调用箭头函数的返回值就作为reduce的返回值
    },
    isAll() {
      if (this.total == this.doneTotal && this.doneTotal > 0) return true;
      return false;
      //return this.total==this.doneTotal
    },
  },
  methods: {
    checkAll(e) {
      this.checkAllTodo(e.target.checked);
      //还是得动app里的数据,得this.checkAllTodo，methods又没有
    },
    clearAll() {
      this.clearAllTodo();
    },
  },
};
</script>

<style scoped>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>
